Growth kinetics in spherulitic crystallization of explosives 3-nitro-1,2,4-triazol-5-one (NTO) in water-N-methylpyrrolidone (NMP) are explored by seeded cooling crystallization. The effects of supersaturation, temperature and solvent composition were investigated. The orders of the growth for NTO spherulites with respect to supersaturation were found to be 3,62, 2.67 and 2.04, and the activation energies for formation of NTO spherulites were determined as about 77.5, 61.0 and 51.5 kJ/mol for the water-NMP ratio of 1.8, 3.0 and 8.0, respectively. Water acts as an accelerator of spherulitic NTO growth from ternary NTO-water-NMP system by enhancing aggregation of crystals. As cooling rate and NMP content in solvent were increased, compactness and sphericity of NTO spherulites were increased. Spherical spherulites of NTO in average diameter ranging from 30 to 300 mum were crystallized by adjusting the composition of co-solvent and the agitation rate.